You need to use the body parameter:

    "parameters": [
      {
        "in": "body",
        "name": "body",
        "description": "Pet object that needs to be added to the store",
        "required": false,
        "schema": {
          "$ref": "#/definitions/Pet"
        }
      }
    ],

and #/definitions/Pet is defined as a model:

"Pet": {
  "required": [
    "name",
    "photoUrls"
  ],
  "properties": {
    "id": {
      "type": "integer",
      "format": "int64"
    },
    "category": {
      "$ref": "#/definitions/Category"
    },
    "name": {
      "type": "string",
      "example": "doggie"
    },
    "photoUrls": {
      "type": "array",
      "xml": {
        "name": "photoUrl",
        "wrapped": true
      },
      "items": {
        "type": "string"
      }
    },
    "tags": {
      "type": "array",
      "xml": {
        "name": "tag",
        "wrapped": true
      },
      "items": {
        "$ref": "#/definitions/Tag"
      }
    },
    "status": {
      "type": "string",
      "description": "pet status in the store",
      "enum": [
        "available",
        "pending",
        "sold"
      ]
    }
  },
  "xml": {
    "name": "Pet"
  }
},

Ref: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/2_0/petstore.json#L35-L43

OpenAPI/Swagger v2 spec: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#parameter-object

For OpenAPI v3 spec, body parameter has been deprecated. To define the HTTP payload, one needs to use the requestBody instead, e.g. https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/3_0/petstore.json#L39-L41

OpenAPI v3 spec: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#requestBodyObject

I made it work with:

    post:
      consumes:
        - application/json
      produces:
        - application/json
        - text/xml
        - text/html
      parameters:
        - name: body
          in: body
          required: true
          schema:
            # Body schema with atomic property examples
            type: object
            properties:
              testapi:
                type: object
                properties:
                  messageId:
                    type: string
                    example: kkkk8
                  messageDateTime:
                    type: string
                    example: '2014-08-17T14:07:30+0530'
              testapiBody:
                type: object
                properties:
                  cameraServiceRq:
                    type: object
                    properties:
                      osType:
                        type: string
                        example: android
                      deviceType:
                        type: string
                        example: samsung555
            # Alternatively, we can use a schema-level example
            example:
              testapi:
                testapiContext:
                  messageId: kkkk8
                  messageDateTime: '2014-08-17T14:07:30+0530'
                testapiBody:
                  cameraServiceRq:
                    osType: android
                    deviceType: samsung555

It's an old question but since I haven't found a solution online here how I to customized the example value in the swagger documentation produce automatically by the java annotations. I use swagger 2.0 and springfox.version 2.10.5.

The Idea is documenting the class of the request parameter that has the @RequestBody annotation. for example my method is

    @ApiOperation(
              value = "Start ListBuilder extraction",
              response = ExtractionLogEntity.class,
              produces = "application/json"
            )
    @PostMapping("/extraction/start")
    public ExtractionLogEntity startTask(
        @RequestBody(required = true) ExtractionRequest request,

In order to expose request json object example I added a @ApiModelProperty(example = "...") annotation to the properties of ExtractionRequest .

   @ApiModelProperty(example = "[{ 'field':'value'}]")
    @NotNull
    private  List<ListBuilderFieldEntity> fields;

   @ApiModelProperty(example = "1000")

    private  String ied;
   @ApiModelProperty(example = "US")
    private  String codebase;

And that's the result